This invention relates generally to joints for glass pipes, and in particular to an interface gasket which is interposable between the adjoining ends of glass pipes.
In industrial and institutional processes as well as in laboratory and pilot plant operations, glass pipes and fittings satisfy the need for high visibility of the flowing product throughout the process and also assure the utmost cleanliness in processing conditions. The pipes and fittings are preferably made of borosilicate glass. This type of glass is capable of operating at temperatures up to 450.degree.F, and because of its heat shock resistance, it tolerates a quick transition from cleaning steam to the flow of cold liquid. Borosilicate glass pipe is highly resistant to chemical attack and neither corrosion nor scale will form on the smooth inner wall thereof.
Glass pipes and fittings are available commercially in various shapes and sizes. Thus one may obtain straight glass pipe in a range of lengths and diameters, and pipes can also be had having a U-bend, a Y-shape or a cross formation. But in all instances the ends of the pipes or fittings have a conical formation to facilitate coupling to like pipes or other process equipment such as glass valves and tanks. Such couplings are generally effected by means of flange sets.
The standard flange set includes a pair of metal flanges having central openings which are large enough to accommodate the ends of the pipes for which they are intended, and a pair of inserts in the form of split rings adapted to surround the conical pipe ends to provide seats for the flanges. Also provided is a group of bolts which pass through bores in the flanges, the bolts being locked to the flanges by nuts. The bolts interconnect the flanges and serve to compress a gasket interposed between the pipe ends and serving to seal the joint therebetween.
The usual interface gasket is formed by a one-piece annular Teflon sheath having a core of Neoprene asbestos or other suitable material, the inner diameter of the sheath being the same as that of the pipe, so that there is no constriction of flow at the pipe joint if the gasket is properly aligned. In order to properly locate the gasket with respect to the pipe, the core is extended beyond the sheath to provide at least three or four tongues having bores therein which register with bores in the flanges.
Thus in assembling a flange set on the ends of adjoining glass pipes, first the insert and flanges are mounted on the pipe ends and then the gasket is interposed between the ends, the bores on the gasket core being aligned with corresponding bores on the flanges. Finally the bolts are passed through the flange bores, two or more of the bolts also going through the bores in the tongues on the gasket, so that when the nuts are applied to the bolts to interconnect the flanges, the gasket is compressed between the pipe ends.
Commercially available flange sets for specified pipe ends are not identical, even though they are intended to fit pipe ends having the same internal and external diameter. Thus in some sets the metal flanges have a generally triangular form and have bores at the corner angles, the three bores lying at equi-spaced points on a bolt circle. In other instances, the flanges have a square configuration, with bores at the four corners. In still other cases, the flanges are in circular disc form.
Hence an interface gasket intended for triangular flanges must have its tongues and bores designed to cooperate with such flanges, while gaskets intended for square flanges must be designed accordingly. Thus, unless the gasket used with a flange set is appropriate to the flanges, there is a danger of gasket misalignment and blow out, even though the gasket otherwise matches the ends of the pipes to be joined.
One must, therefore, with existing types of flange sets, maintain a large inventory of interface gaskets to cooperate with the various types of interface gaskets to cooperate with the various types of flanges in stock. It is not possible to use an interface gasket whose internal diameter matches that of the pipes to be joined unless the alignment holes in the gasket also match the bore holes in the cooperating flanges.